With Tory MPs continuing to agitate for the introduction of a married couple's tax allowance, Treasury minister David Gauke has written a letter to backbenchers reassuring them that the government "will legislate for this in this Parliament".

The policy, as outlined in the 2010 Conservative manifesto, would allow individuals not using all of their personal tax allowance (because their income is less than the current threshold of £9,440) to transfer up to £750 of this unused allowance to their spouse or civil partner, reducing the latter's tax bill by up to £150. It would apply only to couples where the higher-income member is a basic rate taxpayer, with gains tapered away from higher earners. The proposal was included in the Tory manifesto and the coalition agreement provided the Lib Dems with the right to abstain, so Tory MPs are understandably angered by the government's tardiness. But as I show below, there are at least five good reasons why George Osborne (one of the most socially liberal MPs) shows every sign of wanting to abandon it.

1. Only a third of married couples will​ benefit

Despite the broad promise to "recognise marriage" in the tax system, most married couples won't gain from it. In 2010, the IFS estimated that just four million out of 12.3 million married couples would benefit (at a cost of £550m), including only 2.5 million of the 8.7 million married couples with someone in work. The remaining 1.5 million gainers are mostly married pensioners. As the IFS noted, "The policy is not, therefore, a general recognition of marriage in the tax system, as it affects only 32% of married couples and 29% of non-pensioner married couples."

The policy could, of course, be redesigned so that all or most married couples benefit but this, not least for the fiscally conservative Osborne, would be prohibitively expensive.

2. It discriminates against single parents, widows and widowers and more

In his recent GQ article, Andy Coulson described the perception that David Cameron does not like single parents as "electoral halitosis", but this policy unambiguously discriminates against them. Among those who also don't gain from the policy, as Don't Judge My Family notes, are widows and widowers, people who leave abusive relationships and working couples (discussed below). Is Osborne comfortable with tilting the tax system against them? In addition, if, as previously suggested, those in civil partnerships benefit from the measure, it will become even harder for the government to argue against introducing them for heterosexual couples (a policy that, unlike equal marriage, really would undermine marriage).

3. It will reduce work incentives

Through policies such as reserving childcare support for dual-earner couples, Osborne has sought to increase work incentives, but this measure will reduce them. Since only those couples with one earner with an income above the personal allowance will benefit, it will encourage actual or potential second earners to stay at home.

4. There's no evidence that marriage improves child outcomes

One of the main justifications for the policy is that marriage is beneficial for children. As Iain Duncan Smith has argued, "You cannot mend Britain’s broken society unless you support and value the institution which is at the heart of a stable society". But while children born to married couples have better developmental outcomes than those born to cohabiting couples, there's no evidence that this is due to marriage itself. Instead, as the IFS and others have argued, it is more likely due to the fact that better educated and higher-earning couples are more likely to get married. The right has confused correlation and cause.

5. It will further complicate the tax system

Osborne has made much of his commitment to simplifying the tax system, but this proposal will create a new layer of complexity. To summarise, it will introduce a transferable allowance restricted to a third of married couples, capped at £750 and tapered away from higher-rate taxpayers. As the IFS points out, "Simpler ways to provide support to low- to middle income married couples would include introducing a married couples’ ‘premium’ into working tax credit and pension credit."

The Brexit Beartraps, #2: Could dropping out of the open skies agreement cancel your holiday?

So what is it this time, eh? Brexit is going to wipe out every banana planet on the entire planet? Brexit will get the Last Night of the Proms cancelled? Brexit will bring about World War Three?

To be honest, I think we’re pretty well covered already on that last score, but no, this week it’s nothing so terrifying. It’s just that Brexit might get your holiday cancelled.

What are you blithering about now?

Well, only if you want to holiday in Europe, I suppose. If you’re going to Blackpool you’ll be fine. Or Pakistan, according to some people...

You’re making this up.

I’m honestly not, though we can’t entirely rule out the possibility somebody is. Last month Michael O’Leary, the Ryanair boss who attracts headlines the way certain other things attract flies, warned that, “There is a real prospect... that there are going to be no flights between the UK and Europe for a period of weeks, months beyond March 2019... We will be cancelling people’s holidays for summer of 2019.”

He’s just trying to block Brexit, the bloody saboteur.

Well, yes, he’s been quite explicit about that, and says we should just ignore the referendum result. Honestly, he’s so Remainiac he makes me look like Dan Hannan.

But he’s not wrong that there are issues: please fasten your seatbelt, and brace yourself for some turbulence.

Not so long ago, aviation was a very national sort of a business: many of the big airports were owned by nation states, and the airline industry was dominated by the state-backed national flag carriers (British Airways, Air France and so on). Since governments set airline regulations too, that meant those airlines were given all sorts of competitive advantages in their own country, and pretty much everyone faced barriers to entry in others.

The EU changed all that. Since 1994, the European Single Aviation Market (ESAM) has allowed free movement of people and cargo; established common rules over safety, security, the environment and so on; and ensured fair competition between European airlines. It also means that an AOC – an Air Operator Certificate, the bit of paper an airline needs to fly – from any European country would be enough to operate in all of them.

Do we really need all these acronyms?

No, alas, we need more of them. There’s also ECAA, the European Common Aviation Area – that’s the area ESAM covers; basically, ESAM is the aviation bit of the single market, and ECAA the aviation bit of the European Economic Area, or EEA. Then there’s ESAA, the European Aviation Safety Agency, which regulates, well, you can probably guess what it regulates to be honest.

All this may sound a bit dry-

It is.

-it is a bit dry, yes. But it’s also the thing that made it much easier to travel around Europe. It made the European aviation industry much more competitive, which is where the whole cheap flights thing came from.

In a speech last December, Andrew Haines, the boss of Britain’s Civil Aviation Authority said that, since 2000, the number of destinations served from UK airports has doubled; since 1993, fares have dropped by a third. Which is brilliant.

Brexit, though, means we’re probably going to have to pull out of these arrangements.

Stop talking Britain down.

Don’t tell me, tell Brexit secretary David Davis. To monitor and enforce all these international agreements, you need an international court system. That’s the European Court of Justice, which ministers have repeatedly made clear that we’re leaving.

So: last March, when Davis was asked by a select committee whether the open skies system would persist, he replied: “One would presume that would not apply to us” – although he promised he’d fight for a successor, which is very reassuring.

We can always holiday elsewhere.

Perhaps you can – O’Leary also claimed (I’m still not making this up) that a senior Brexit minister had told him that lost European airline traffic could be made up for through a bilateral agreement with Pakistan. Which seems a bit optimistic to me, but what do I know.

Intercontinental flights are still likely to be more difficult, though. Since 2007, flights between Europe and the US have operated under a separate open skies agreement, and leaving the EU means we’re we’re about to fall out of that, too.

Surely we’ll just revert to whatever rules there were before.

Apparently not. Airlines for America – a trade body for... well, you can probably guess that, too – has pointed out that, if we do, there are no historic rules to fall back on: there’s no aviation equivalent of the WTO.

The claim that flights are going to just stop is definitely a worst case scenario: in practice, we can probably negotiate a bunch of new agreements. But we’re already negotiating a lot of other things, and we’re on a deadline, so we’re tight for time.

In fact, we’re really tight for time. Airlines for America has also argued that – because so many tickets are sold a year or more in advance – airlines really need a new deal in place by March 2018, if they’re to have faith they can keep flying. So it’s asking for aviation to be prioritised in negotiations.

The only problem is, we can’t negotiate anything else until the EU decides we’ve made enough progress on the divorce bill and the rights of EU nationals. And the clock’s ticking.

This is just remoaning. Brexit will set us free.

A little bit, maybe. CAA’s Haines has also said he believes “talk of significant retrenchment is very much over-stated, and Brexit offers potential opportunities in other areas”. Falling out of Europe means falling out of European ownership rules, so itcould bring foreign capital into the UK aviation industry (assuming anyone still wants to invest, of course). It would also mean more flexibility on “slot rules”, by which airports have to hand out landing times, and which are I gather a source of some contention at the moment.

But Haines also pointed out that the UK has been one of the most influential contributors to European aviation regulations: leaving the European system will mean we lose that influence. And let’s not forget that it was European law that gave passengers the right to redress when things go wrong: if you’ve ever had a refund after long delays, you’ve got the EU to thank.

So: the planes may not stop flying. But the UK will have less influence over the future of aviation; passengers might have fewer consumer rights; and while it’s not clear that Brexit will mean vastly fewer flights, it’s hard to see how it will mean more, so between that and the slide in sterling, prices are likely to rise, too.

It’s not that Brexit is inevitably going to mean disaster. It’s just that it’ll take a lot of effort for very little obvious reward. Which is becoming something of a theme.

Still, we’ll be free of those bureaucrats at the ECJ, won’t be?

This’ll be a great comfort when we’re all holidaying in Grimsby.

Jonn Elledge edits the New Statesman's sister site CityMetric, and writes for the NS about subjects including politics, history and Brexit. You can find him on Twitter or Facebook.